Monday, December 15, 2008

The Iberian Lynx is now the most endangered cat in the world with only about 160 animals remaining in the wild and, despite extensive research and millions of Euros spent in decades of protection, nothing seems capable to stop this decline. But a totally new approach to its conservation is now being proposed by Portuguese and Spanish researchers in an article to appear in the journal Diversity and Distributions¹ where it is defended that the key to the lynx survival is the restoration of the animal original habitat as well as the full genetic range of its prey, the European rabbit. The work is based on the study of the geographical distribution of two interacting species over time, and reveals how this type of approach can bring a total different view into the conservation of species resistant to more traditional interventions, such as the lynx.

** This article is the result of a project for the divulgation of portuguese science" http://www.cienciahoje.pt/1455"

In the last two decades the Iberian Lynx, which was once widespread in the Iberian Peninsula, has been steadily disappearing while resisting every conservational attempt to boost its numbers, which are holding mostly due to artificial feeding. In an attempt to try and stop what is starting to look like an inexorable path to extinction Raimundo Real, A. Márcia Barbosa, Miguel Delibes and colleagues working in at the University of Evora, Portugal, the University of Malaga and the Doñana Biological Station, Spain and at Imperial College, London decided to look into the combined history of the lynx and its almost exclusive prey, the European rabbit, which, interestingly, was known to have suffered a drastic population reduction as result of disease during the 1980s, exactly when the steady decline of the lynx has become more apparent.

Moreover, the rabbit has two subspecies/lineages that are geographically separated – one in the northeast and the one in southwest of the Iberian Peninsula – and it is also in the 80s that the lynx becomes confined to the southwest territory and its corresponding rabbit lineage. Real, Barbosa, Delibes and colleagues’ idea was to test if the current lynx struggle could be, not only a problem with rabbit numbers as already suspected, but also with a lack of prey’s diversity.

To test this hypothesis the researchers developed two mathematical models – one for each species - relating sets of environmental factors – such as climate, state of the soil, etc – to population abundance. These models could then be used to test if changes in the environment or instead variations in the rabbit populations were the reason behind the recent lynx disappearances

What the researchers found was that the new developed lynx environmental model (that predicts lynx abundance according to the set of environmental conditions occurring at a specific moment in time) although capable of accurately predicting the lynx abundance in 1958, it was not able to correctly calculate the 1989 population. This strongly suggested that, at that moment in time, some other, non-environmental factor was already affecting lynx viability. And in fact, when the researchers combined the rabbit and the lynx models – since the lynx preys almost exclusively on the European rabbit, the rabbit model could be used to test food as a limiting factor for the lynx – the numbers obtained fitted perfectly those currently measured in the wild suggesting that indeed rabbit/food availability was conditioning the lynx present growth.

Interestingly, Real and colleagues also found a negative association between the southwest rabbit lineage – the only one currently available to the lynx – and the optimum rabbit living conditions suggesting that this subspecies is not thriving (contrary to the results found for the northeast lineage) compromising even more the lynx chances of success.

Transfer of northeast rabbits into the area now occupied by the lynx is not the solution for the lynx problem because, first it is not clear how favourable these areas are for rabbit thriving, and second the two rabbit subspecies have low inter- fertility and if mixed can lead to a declining in rabbits numbers that risk pushing the lynx even closer to extinction.

What Real, Barbosa, Delibes and colleagues propose, as consequence of these findings, is a totally different conservation approach for the lynx problem, involving the restoration of the animal to the territories habited by the east rabbits so the predator can have access to the full genetic range of its prey, while allowing too the re-establishment of old ecological interrelationships, hopefully, maximising the lynx chances of survival.

This solution takes into account for the first time the crucial fact that the rabbit and the lynx have been historically connected for hundreds of years sharing a geography and experiencing a multitude of interactions which are not easy to replace or even fully understand. Additionally, by allowing the lynx access to what appears to be the most successful/viable Iberian rabbit it also gives the predator a better chance of survival if a new natural disaster occurs. Hopefully this might help the lynx avoid to becoming the first feline extinct since the sabre-toothed tiger 10,000 years ago.